There exists in the literature considerable confusion and conflict regarding the ability of growing bone to remodel in response to torsional changes. This study proposes to investigate the morphologic changes in the femora of immature dogs following a subtrochanteric osteotomy. The specific contribution of each epiphysis and metaphysis will be investigated by both radiographic and histologic means. Methods are described for specifically determining the site and amount of derotation occuring over a follow-up period of 5-6 months. It is hoped that this information will add to the clincian's understanding of torsional remodelling following either fracture or osteotomy.